The present invention relates to a recycled resin composition, more specifically, to a recycled resin composition effectually utilizing pulverized materials made from a recovered molded article such as sprues or runners generated especially at the time of producing molded products and to a method for producing the recycled resin compositions.
Thermoplastic resins are widely used since they have various excellent properties such as moldability, electrical insulation property, mechanical property or the like. One of the advantages of the thermoplastic resins is that material can be efficiently used. Other molded articles (also referred to as recovered molded articles) than final products, such as sprues, runners or any molded products which does not satisfy specifications (off specifications), are generated at the time of producing products by injection molding.
In recent years, various types of products have become smaller and lighter, and parts (molded products) used in such products have also become smaller. Therefore, resin compositions having an excellent mold ability are widely utilized in such parts, many of which are small and thin. In the case of producing such small parts (molded products), a weight ratio of sprue and runner in the total weight of the molded product is large. If recovered molded articles such as sprue or runner are discarded, a yield efficiency of raw material resin compositions becomes lower. Therefore, the recovered molded articles are pulverized to be a pulverized material (referred to as a recycled material) without being discarded. This recycled material and a raw material resin composition pellet (virgin pellet) maybe simply mixed and be subjected to injection molding. However, the molded product obtained from such a resin mixture suffers from degradation of physical properties such as the mechanical property, flame-retardant property or the like, and causes various problems such as defective feeding to a molding apparatus.
One reason for degradation of physical properties includes that pulverized materials contains much powder and the size of granules is unequal to the pellets of the raw material resin compositions. The pulverized materials (a recycled material) may be melted, kneaded, extruded and cut to be re-pelletized in an extruder, and then may be blended with a virgin pellet and subjected to injection molding, but the thermal decomposition, degradation, change of properties of the material can not be avoided, and the degradation of the physical properties of the molded products can not be avoided.
It is an object of the present invention to provide a recycled resin composition having physical properties, a feeding property and a moldability which are comparative with the raw material resin composition, even when a ratio of recycled material in the recycled resin composition used as molding material is increased.
The present inventors have been diligently studied to accomplish the above-mentioned object, and as a result, they have found that a recycled resin composition obtained by compounding a raw material resin, at least one kind of additives for resin, and a pulverized material of a recovered molded article such as sprue or runner generated at the time of producing molded products from a raw material resin composition and/or a recycled resin composition, have almost the same performance as that of a raw material resin composition made from a raw material resin and additives for resin. The present invention has been completed on the basis of these findings.
According to the present invention, there is provided a recycled resin composition obtained by compounding a mixture containing (a) a raw material resin, (b) at least one kind of additives for resin, and (c) a pulverized material of a recovered molded article generated at the time of molding of a raw material resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin and/or a recycled resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin.
Preferably, the recycled resin composition of the present invention is in a pelletized form which is obtained by compounding the mixture in an extruder, etc, and cutting the mixture.
Preferably, the recycled resin composition of the present invention has a composition substantially the same as that of (c) a pulverized material of a recovered molded article generated at the time of molding of a raw material resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin and/or a recycled resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin. Preferably, the raw material resin composition composed of (a) the raw material resin and (b) at least one kind of the additives for resin has a composition substantially the same as that of (c) the pulverized material of a recovered molded article generated at the time of molding of a raw material resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin and/or a recycled resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin.
Preferably, the recycled resin composition of the present invention is obtained by compounding the mixture containing 25 to 95 parts by weight of a total amount of (a) the raw material resin and (b) at least one kind of the additives for resin, and 75 to 5 parts by weight of (c) the pulverized material of a recovered molded article generated at the time of molding of a raw material resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin and/or a recycled resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin.
Preferably, (a) the raw material resin is one resin or a mixture of two or more resins which are selected from a group consisting of polyester resin, polycarbonate resin, polyamide resin, polyoxymethylene resin, polyphenylene ether resin, polyolefin resin, polystyrene based resin, and polyphenylene sulfide resin.
Preferably, the recycled resin composition of the present invention comprises a glass fiber as one kind of (b) the additives for resin.
Preferably, (c) the pulverized material has a particle size of 0.1 to 50 mm, more preferably 0.2 to 30 mm, and even more preferably 0.3 to 25 mm. If the particle size is too large or too small, the blending of the pulverized material and the raw material resin composition becomes difficult, and the defective feeding tends to occur, and it is not preferred.
When the recycled resin composition according to the present invention comprises a glass fiber as one kind of (b) the additives for resin, (c) the pulverized material preferably has a particle size of 0.5 to 50 mm, more preferably 0.7-30 mm, and even more preferably 1-25 mm.
Preferably, a breaking strength of the molded product made from the recycled resin composition is 80% or higher, more preferably 90% or higher of that of a molded product made from the raw material resin composition.
Preferably, an elongation at break of the molded product made from the recycled resin composition is 80% or higher, more preferably 90% or higher of that of a molded product made from the raw material resin composition.
Preferably, a flexural strength of the molded product made from the recycled resin composition is 80% or higher, more preferably 90% or higher of that of a molded product made from the raw material resin composition.
Preferably, a flexural modulus inelasticity of the molded product made from the recycled resin composition is 80% or higher, more preferably 90% or higher, particularly preferably 95% or higher of that of a molded product made from the raw material resin composition.
Preferably, a flammability (Flame class), prescribed in UL 94, of the molded product made from the recycled resin composition is substantially similar with that of a molded product made from the raw material resin composition.
According another aspect of the present invention, there is provided a molded product produced from the recycled resin composition of the present invention.
According to further aspect of the present invention, there is provided a method for producing the recycled resin composition of the present invention, which comprises a step of compounding the mixture containing (a) a raw material resin, (b) at least one kind of the additives for resin, and (c) a pulverized material of a recovered molded article generated at the time of molding of a raw material resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin and/or a recycled resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin.
In the method for producing the recycled resin composition of the present invention, the recycled resin composition preferably has a composition substantially the same as that of (c) the pulverized material of a recovered molded article generated at the time of molding of a raw material resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin and/or a recycled resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin, and a raw material resin composition composed of (a) the raw material resin and (b) said at least one kind of the additives for resin preferably has a composition substantially the same as that of (c) the pulverized material of a recovered molded article generated at the time of molding of a raw material resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin and/or a recycled resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin.
According to still further aspect of the present invention, there is provided a method for recycling a resin which comprises the steps of: collecting (c) a pulverized material of a recovered molded article generated at the time of molding of a raw material resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin and/or a recycled resin composition comprising (a) said raw material resin and (b) said at least one kind of additives for resin, and compounding a mixture containing (a) a raw material resin, (b) at least one kind of the additives for resin, and (c) the thus collected pulverized material to produce a recycled resin composition.